Re: Window Function "Run Conditions"

Hi David:

Thanks for the patch.

On Wed, Aug 18, 2021 at 6:40 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> On Tue, 17 Aug 2021 at 03:51, Zhihong Yu <zyu(at)yugabyte(dot)com> wrote:
> > + if ((res->monotonic & MONOTONICFUNC_INCREASING) == MONOTONICFUNC_INCREASING)
> >
> > The above can be simplified as 'if (res->monotonic & MONOTONICFUNC_INCREASING) '
>
> True. I've attached an updated patch.
>
> David

Looks like we need to narrow down the situation where we can apply
this optimization.

SELECT * FROM
(SELECT empno,
salary,
count(*) over (order by empno desc) as c ,
dense_rank() OVER (ORDER BY salary DESC) dr

FROM empsalary) emp
WHERE dr = 1;

In the current master, the result is:

empno | salary | c | dr

-------+--------+---+----

8 | 6000 | 4 | 1

(1 row)

In the patched version， the result is:

empno | salary | c | dr

-------+--------+---+----

8 | 6000 | 1 | 1

(1 row)

--
Best Regards
Andy Fan (https://www.aliyun.com/)